Field of the Invention
The present invention relates to assistance for towing vehicles and, in particular, to a structure and method for detecting when the brakes of a towed vehicle are locked by a brake activation system.
Related Art
It is often convenient to tow one vehicle behind another. While the towed vehicle can be carried on a separate trailer, the trailer adds additional weight to the combination. For braking, a heavy trailer typically provides a separate braking system that can be controlled by the tow vehicle through a standardized interface. The trailer's brakes can significantly reduce the stopping distance of the combination by aiding the tow vehicle in stopping the combination. Unlike a trailer, a typical towed vehicle, such as an automobile, a car, or a truck, does not have a trailer braking system interface. To reduce stopping distances, however, auxiliary braking systems have been developed to activate the towed vehicle's independent braking system.
Auxiliary braking controller systems come in many different configurations. Some systems connect to a trailer brake controller on the tow vehicle. The system then emulates the response that would be provided by a trailer. Others act independently of the towed vehicle using sensors to determine when the tow vehicle is slowing down. These sensors may be coupled to the hitch bar or coupled in another way to the two vehicles. Recently accelerometers connected with the towed vehicle have been used to determine when the towed vehicle is being slowed by the tow vehicle. There are also different ways to activate the towed vehicle's brake system. More complex systems electronically or hydraulically connect to the brake system to activate it or to boost pressure. A simpler system simply attaches to the towed vehicle's brake pedal and pushes the pedal to activate the brakes.
For use with recreational vehicles, portable auxiliary braking systems have been developed that can be placed on or in front of the driver's seat of the towed vehicle and then be attached to the brake pedal. Such systems may also require connections for power, control, and auxiliary safety systems. When the user has arrived at a parking destination, the portable system is removed from the towed vehicle so that the towed vehicle can be driven. When the user is ready to move to a new destination, the portable system is reinstalled. These same systems may also be used to tow vehicles using other vehicles in other contexts separate and apart from recreational vehicle use.
Since the braking system might be installed and removed several times a day in order to drive the towed vehicle, there is a constant risk that an operator may inadvertently install the system into the vehicle incorrectly. With a system that attaches to the brake pedal, there is a risk that the brake pedal will be pushed when it should not be pushed or that the system will lock the brakes and not release. In either event, the towed vehicle's brakes, tires, and other parts may be damaged or worn.